Cordless tools including interchangeable battery units are widely known in the prior art, as exemplified for example by U.S. Pat. Nos. 3,043,996; 3,381,636; 3,533,119; 3,186,878; and 3,757,194. However, the general conception of the ultimate product employed in each of these patents has been that of simply substituting a packaged battery-type source of energy as an alternative to the conventional line cord set provided with corded power tools. Thus, the structures described by these patents essentially describe completed, self-contained tools with a receptacle provided therein for receiving the battery.
In the co-pending application of Owings, Beckering, and Bunyea, Ser. No. 500,131,filed concurrently herewith and assigned to the assignee of this application, the specification of which is incorporated herein by reference, a modular system of power tools is described and claimed wherein a specific rechargeable handle module which incorporates rechargeable batteries, a hand grip and a switch may be coupled with a wide variety of interfitting tool heads having various output means. The tool heads generally include a motor, a transmission and an output device such as grass shear blades, drill chuck, etc. The system may also include tool heads which do not utilize a motor such as a flashlight head, a soldering iron, etc. The Owings et al application describes and claims this modular system as a basic concept including a variety of specific novel features which contribute to the practical utilization of the system such as the provision of a large pilot surface to provide for stable interconnection of the modules, the provision of dovetail means to further contribute to the mechanical stability, the provision of exposed electrical contacts which automatically complete appropriate electrical circuits, the provision of a closed loop handle module for strength and ease of manufacture, and the provision of lock-off means to prevent accidental energization of the tool output means during assembly of the respective modules.
The present invention describes and claims the preferred embodiment of the invention set forth in the aforementioned Owings et al application. In particular, the specific mechanical and electrical construction features set forth hereinafter, in the context of the basic modular system, further enhance the practicality, utility and other advantages of the system. Thus, in accord with the present invention, a mechanical-electrical assembly for a modular system of power tools is provided wherein a male-female dovetail interlock tapered in the direction of assembly to enable maximum ease of assembly and maximum structural stability. The system further includes a plurality of exposed electrical contacts disposed between the corresponding dovetail members and arranged so as to provide automatic wiping engagement as the modules are assembled. In further accord with this invention, the terminals of the power handle module extend internally to provide for switching action by means of a simple contacting element mounted directly on the trigger member which is engaged by the operator. Further specific aspects of this invention include the provision of an automatically engaged latch for retaining the separate modules in assembled relation and, on appropriate modules, an automatic override to disengage the lock-off member during assembly.
From the foregoing, it will be apparent that the objects of the present invention include the provision of a simple, low cost interconnection structure for mating, independent modules of a modular power tool system which permits easy assembly while also providing maximum electrical and mechanical integrity of the overall system.
Further objects and advantages of this invention will become apparent as the description and illustration thereof proceed.